CTLA Trunk Formula
Tree Appraisal Method

Appraised Value = Base Value × (Tree CSA ÷ Replacement CSA) × Species Rating × Condition × Location. CSA is cross-sectional area at breast height — π × (DBH ÷ 2)² — so the core of the formula is a ratio: how much bigger is this tree's trunk than the largest tree you could realistically buy and plant as a replacement. That ratio gets scaled down by three factors, each expressed as a percentage: how desirable the species is in that region, what shape the tree is in, and how much the site itself adds or subtracts from the tree's value.

A large, healthy, well-placed specimen of a locally valued species can appraise at tens of thousands of dollars under this method — which is exactly why insurers, courts, and municipalities lean on a standardized formula instead of a number someone made up. The formula doesn't remove judgment entirely (species rating and location factor are still assigned by the appraiser, usually from a regional guide), but it fixes the *structure* of the calculation so two appraisers working the same tree land on comparable numbers.

CTLA publishes the Trunk Formula Method as part of the Guide for Plant Appraisal, now in its 10th edition through the International Society of Arboriculture. It's the reference method for insurance claims after storm damage or construction injury, tort cases where a tree was damaged or removed without consent, and tax or real-estate assessments that need a defensible tree value rather than a rough guess.

An appraisal is only as good as the DBH, condition, species rating, and location factor it's built from — get any of those wrong in the field and the appraised value is wrong too, no matter how careful the formula is. See how LogLog records appraisal fields alongside the rest of a tree's record, tied to the same pin as species, DBH, and condition.